1. Field of the Invention
The present invention relates to a nitride semiconductor light emitting device and a method of manufacturing the same, and more particularly, to a nitride semiconductor light emitting device that includes an n-type electrode having thermal stability and excellent electrical characteristics without heat treatment and a method of manufacturing the same.
2. Description of the Related Art
A light emitting diode (LED) is one of semiconductor light emitting devices. When a current is applied, the LED can generate light of various colors by recombination of electrons and holes in a p-n junction between p-type and n-type semiconductors. When compared with a filament-based light emitting device, the LED has longer lifetime, low power consumption, excellent initial driving characteristics, high vibration resistance, and high tolerance for repetitive power switching. Thus, there has been an increasing demand for the LEDs. These days, group III nitride semiconductors that can emit light in short-wavelength region, such as a series of blue, have attracted attention.
FIG. 1 is a cross-sectional view illustrating a nitride semiconductor light emitting device according to the related art.
A nitride semiconductor light emitting device 10 includes a sapphire substrate 14, an n-type nitride semiconductor layer 11, an active layer 12, a p-type nitride semiconductor layer 13, a p-type ohmic contact layer 18, and an n-type ohmic contact layer 15, which are sequentially grown on the sapphire substrate 14. Here, the n-type ohmic contact layer 15 is formed on a region formed by etching the n-type nitride semiconductor layer 11. The nitride semiconductor light emitting device 10 further includes n-type and p-type electrodes 16a and 16b. 
The semiconductor light emitting device 10 has a light emitting structure between the n-type and p-type electrodes 16a and 16b. That is, the semiconductor light emitting device 10 is a horizontal light emitting device. Light is generally emitted to the outside through the p-type ohmic contact layer 18.
In this case, then-type ohmic contact layer 15 is formed of Ti, Al, or the like, which has a relatively low work function, to form an ohmic contact with the n-type nitride semiconductor layer 11. Alternatively, the n-type ohmic contact layer 15 may include a stacked structure of Ti and Al.
In general, in order to obtain a structure having thermal stability, the ohmic contact layer 15 is formed by performing heat treatment at a temperature of 400° C. or more. However, the heat treatment may deteriorate the p-type ohmic contact layer 18 or the active layer 12 to reduce device characteristics and further increase manufacturing costs due to the heat treatment.